Coming from a different perspective on this...
There are virtually no resources (save online forums such as this) for Non sikhs who marry sikhs and DESIRE to raise their children sikh. If you live far away from your wives family, or her family is not particularly religious, you are kind of out of luck. Sangat at gurdwaras do not want to touch this issue, at least at the gurdwaras I have been to. You have basically no resources, no organized framework to catch the children of these intermarriages and help them. Other religions do have these systems in place.
Someone gave the jews as an example. Jews actively seek to integrate and educate intermarried couples, hence you have fully 50% of jews marrying non jews, yet the culture is still strong and the religion is passed down. In MANY cases, the spouse ends up converting. Google jewish intermarriage, you will be amazed. This has been happening for a very long time.
Intermarriage is going to happen in a multicultural society, it just will. No religion is immune from it. The religion can come out stronger because of it, or weaker, but it happens to every religious community and it will continue to happen to sikhs as well.